Will there be a dramatic difference?

Yes & no or no & yes but definitely not no & no or yes & yes.

You’re not gonna get any useful recommendations here due to the little info you’ve provided about your specific equipment, room, and sound preferences.  Put a little more effort into providing this critical info and you will get something useful here.

yes a parasound will be an upgrade with improved bass control

we are a parasound dealer theA21 is a good amp you want a jc5 which is a much better amplifier then the 21

Dave and Troy

audio intellect nj

parasound dealers

Long ago I (briefly) had a Carver Sunfire Signature II 600 pushing Legacy Signature III speakers, and hated it. Replaced the Sunfire with a Parasound A21, and it was an absolutely massive improvement. Do it! 

Although I don't post much, I can tell you I am A life long (64 year old)carver user. All upgraded by Nelion Audio., I decided to upgrade a bit Got an ARC ref5se pre to replace the Carver pre. Wow!  Next got an ARC ref75se amp.next  More wow!! Then an Aurender A15 to replace Auralic Altair. Ok  thats it, I love tubes. Klipsch Forte III, GRresearch crossovers.

This upgrade sounds phenomenal. My point is having and listening to my Carver gear, which I had since the eighties which isn't the worst, and moving up the ladder was the best decision in my audio journey I ever made. So yes, do it!